If you have been reading about actin binding and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-07-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
Thymosin beta-4 is a 43-residue actin-binding protein found in most mammalian cell types, where it participates in cytoskeletal regulation and cell migration. TB-500 represents only a short fragment of that protein and does not include the remaining residues. Whether the isolated fragment reproduces the full range of activities reported for the intact protein remains an open question. Researchers commonly treat the two as related but distinct entities when comparing results.
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
Lyophilised peptide is normally reconstituted with sterile water or a neutral buffer shortly before use. Because repeated freeze-thaw cycles can degrade the material, dividing a reconstituted solution into single-use aliquots is a common practice. Working solutions are usually kept cold and protected from light. The exact shelf life depends on concentration, buffer composition, and handling, so it is often determined empirically rather than assumed.
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
Proposed activity centers on actin sequestration and on the movement of cells during repair processes. In cell culture and animal models, the fragment has been associated with migration, tube formation, and tissue remodeling. These observations are frequently described as preliminary, because most published work uses rodent or in vitro systems rather than controlled human trials. Whether the short fragment reproduces the effects of the full protein remains an open question, and the relationship between dose, route, and measured outcome is not well characterized.
The compound circulates in the literature as a research reagent rather than an approved therapeutic. Regulatory agencies in several countries have not authorized it for medical use, and sporting bodies list related thymosin beta-4 peptides among prohibited substances. Suppliers typically market it with a purity figure and a certificate of analysis, while peer-reviewed clinical reports remain sparse. Discussions therefore often separate laboratory findings from anecdotal reports, and reviewers tend to note the small size and methodological limits of the available studies.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
== History == Physicians historically used odors as a diagnostic indicator to judge a patient's health. Hippocrates saw the breath of patients as a potential indicator in around 400 BCE. Galen, Avicenna, and other physicians considered urine scent alongside color, density, sediments, and more in urinalysis. Urine with a sweet odor was diagnosed as possessing dominating sanguine humor relative to the other three humors; pungent odor as an excessive amount of bile; and foul odor as the presence of ulcers in the urinary tract or development of putrefactive fever, a fever occurring in the humors. VOCs are currently deemed as noninvasive diagnostic biomarkers with the potential for point-of-care (POC) testing and long-term monitoring.
==== Mechanism of action ==== One of the components in nabiximol, tetrahydrocannabinol (THC), weakly stimulates cannabinoid receptor 1(CBR1) and cannabinoid receptor 2 (CBR2) to produce analgesic effect (pain relief). Another component of nabiximol, cannabidiol (CBD), slightly inhibits the proliferation of T cells (a type of immune cells) and the activity of microglia (cells within the brain that regulate neural activity and repair).
Daphne Walker, singer (born 1930). 19 July – Lee Mummery, cricketer (Central Districts) (born 1935). 20 July – Jim Tomlin, artist, musician (Chants R&B), and art educator (Otago Polytechnic) (born 1940). 23 July – Kathryn Smits, Germanist (University of Auckland) (born 1935). 25 July – Ian Leggat, school teacher and university administrator, principal of Hagley High School (1971–1976) and Christchurch Boys' High School (1976–1988), University of Canterbury chancellor (1992–1998) (born 1929). 26 July Ian Carter, sociologist (University of Auckland) (born 1943). Keith Sorrenson, historian (University of Auckland), president of the Citizens' Association for Racial Equality (1971–1973), member of the Waitangi Tribunal (1986–2011) (born 1932). John Werry, child and adolescent psychiatrist (University of Auckland) (born 1931). 29 July – Sir Michael Hill, jeweller, businessman (Michael Hill Jeweller), and philanthropist (born 1938).
Sources: en.wikipedia.org
Treasury where they may be used for other government purposes. Social Security spending will increase sharply over the next decades, largely due to the retirement of the baby boomer generation. The number of program recipients is expected to increase from 44 million in 2010 to 73 million in 2030. Program spending is projected to rise from 4.8% of GDP in 2010 to 5.9% of GDP by 2030, where it will stabilize. The Social Security Administration projects that an increase in payroll taxes equivalent to 1.8% of the payroll tax base or 0.6% of GDP would be necessary to put the Social Security program in fiscal balance for the next 75 years. Over an infinite time horizon, these shortfalls average 3.3% of the payroll tax base and 1.2% of GDP. Various reforms have been debated for Social Security. Examples include reducing future annual cost of living adjustments (COLA) provided to recipients, raising the retirement age, and raising the income limit subject to the payroll tax ($118,500 in 2014). Because of the mandatory nature of the program and large accumulated surplus in the Social Security Trust Fund, the Social Security system has the legal authority to compel the government to borrow to pay all promised benefits through 2036, when the Trust Fund is expected to be exhausted. Thereafter, the program under current law will pay approximately 75–78% of promised benefits for the remainder of the century.
=== Transforming growth factor β (TGF-β) === In normal conditions, alveolar macrophages adhere closely to alveolar epithelial cells, thus inducing the expression of the αvβ6 integrin. Integrins are dimeric cell-surface receptors composed of alpha and beta subunits, which activates TGF-β. TGF-β is a multifunctional cytokine that modulates a variety of biological processes such as cell growth, apoptosis, extracellular matrix synthesis, inflammation, and immune responses. TGF-β tightly regulates anti-inflammatory activity by suppressing pro-inflammatory cytokine production, thereby inhibiting T-lymphocyte function. Integrins avβ6 and avβ8 sequester latent TGF-β to the cell surface, where activation can be tightly coupled to cellular responses to environmental stress in the maintenance of homeostasis; integrins also localize activated TGFβ in the vicinity of the macrophages. Normally mature TGFβ is secreted as a latent complex with its N-terminal fragment, latency-associated peptide (LAP), which inhibits its activity. The latent complex is covalently linked to the extracellular matrix by binding to latent TGF-β-binding proteins. TGF-β is activated by diverse mechanisms in the lung, ultimately involving either proteolysis or conformational alteration of the LAP. αvβ6 integrin is able to mediate activation of TGF-β by binding to TGF-β1 LAP, which serves as a ligand binding site for the integrin, and is an essential component of the TGF-β activation apparatus. Once activated, TGFβ leads to the suppression of macrophage functionality (cytokine production and phagocytosis).
== Signs and symptoms == Children with sJIA are frequently severely unwell when diagnosed. They often have lost weight and are tired, feverish, experiencing myalgia and arthralgia, as well as occasional chest and stomach pain. These characteristics may overshadow the arthritis in the early stages of the disease. The presence of fever at presentation is practically universal in those with sJIA. The distinctive fever pattern associated with sJIA is characterized by temperatures that surge above 39 °C once or twice a day and then quickly fall to normal or below baseline. More than 80% of patients have a salmon-colored macular or maculopapular rash that appears along with their fever. Urticarial rash is less prevalent. The eruption is usually limited to the trunk, neck, and proximal extremities, but it might spread more widely. Macules typically measure less than 5 mm in diameter, while bigger macules may be present with center fading. The degree of erythema varies in the same patient, however, it is usually migratory and nonpruritic. The existence of arthritis must be validated before meeting the diagnostic criteria. Although arthralgias are often present at onset, arthritis may not be visible at first and can develop weeks, months, or even years later. Additionally, there is a wide range of joint involvement, from polyarticular patterns to oligoarticular patterns (four or fewer joints with arthritis). The wrists, knees, and ankles are the joints that are most frequently affected.
Fat or protein in the food or drink will delay absorption and should be avoided. So a glucose tablet is ideal, a candy bar or pastry is not (both contain fat in addition to starch and usually sugar). Orange juice works, but less well than intended, as its main carbohydrate is fructose. See also: Hypoglycemia; insulin shock. Insulin receptors Protein complexes on the surface of a cell that allows the cell to join or bind with insulin that is in the blood. When the vrll membrane receptor and insulin bind, the cell takes up glucose (sugar) from the blood and can use it for energy. Insulin resistance a condition in which a cell is resistant to insulin action, usually as a result of Type 2 diabetes which is characterized by insulin resistance in about two-thirds of the body's cells (those which require insulin in order to absorb glucose from the blood). The result is that the beta cells can no longer regulate body metabolism correctly. Insulin resistance syndrome A syndrome (set of signs and symptoms) resulting from insulin resistance. It is also called metabolic syndrome. Insulin shock A severe condition that occurs when the level of blood glucose (sugar) drops too far and quickly. The signs are shaking, sweating, dizziness, double vision, convulsions, and collapse. Insulin shock may occur when an insulin reaction is not treated quickly enough. In severe cases, brain damage, nerve damage, or even death is possible. Formerly used, in hospitals, as a treatment for some kinds of mental illness. See also: Hypoglycemia; insulin reaction.
Sources: en.wikipedia.org
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
The lyophilised powder is typically held at -20 C or lower in a dry, dark place. Reconstituted solutions are aliquoted and frozen to avoid repeated freeze-thaw cycles.